Self-service equipment such as vending machine and automatic teller machine becomes more and more popular. Generally, the self-service equipment is equipped with a banknote recognition device, wherein the banknote recognition device includes a banknote recognition mechanism used to recognize the authenticity of a banknote and a banknote box used to save a genuine banknote. Since the self-service equipment is unattended, it is necessary to prevent some lawbreakers from sticking foreign matters such as string or belt on the banknote to withdraw the banknote through the string or belt after the banknote is determined to be genuine by the banknote recognition mechanism before the banknote enters the banknote box.
Therefore, a British patent GB20010015038 provides a solution. Referring to FIG. 1, two sides of the banknote passage used for conveying a banknote are provided with a light-emitting component 22′ and a reflector 24 of a paper sensor 16′, wherein the light emitted by the paper sensor 16′ is parallel to the surface of the banknote 40′; a banknote examination component 14′ is arranged perpendicular to the surface of the banknote 40′. After the banknote examination component 14′ examines that the banknote is genuine, that is, the banknote 40′ passes the examination of the banknote examination component 14′, if the paper sensor 16′ detects that there is a matter passing through between the light-emitting component 22′ and the reflector 24′, the system determines that there is a foreign matter entering the banknote passage, that is a string or belt is stuck on the banknote, then the system interrupts the operation and displays transaction failed.
The above solution determines whether the banknote would be withdrawn by detecting a foreign matter attached on the banknote. However, since the foreign matter attached on the banknote generally is a threadlike matter such as string and belt, the detected area is relatively small and the light emitted by the sensor probably can not irradiate the foreign matter; thus, the detection result probably is unreliable and unnecessary loss is easily caused.